The long-term goal of the proposed research is to better understand the mechanisms by which lower extremity alignment and movement impairments contribute to the development of musculoskeletal pain conditions. Utilizing this knowledge, the candidate's long-term career goals are to test the effects of rehabilitation and prevention strategies in people with a variety of musculoskeletal pain conditions. The development plan to achieve these goals consists of training in four major areas: magnetic resonance imaging (MRI), motor control, advanced joint biomechanics, and electromyography (EMG). Guiding the development plan is the candidate's primary advisor, an expert in motor control aspects of musculoskeletal pain development. Additional members of the advisory committee include, experts in MR imaging, musculoskeletal radiology, EMG/biomechanics, rheumatology, and clinical epidimiology. Training will be in the form of structured readings, attendance of course lectures, and structured laboratory and clinical experiences. With full support from the candidate's department chair and dean, the proposed research will be conducted at an academic institution equipped with a 3-dimensional motion analysis laboratory and a MRI applied sciences laboratory. Using chronic patellofemoral pain (pain originating from the articulation between the patella and femur) as an example of a common musculoskeletal pain condition, the proposed studies are designed to test the general hypothesis that patellofemoral pain (PFP) develops in response to abnormal patellofemoral joint contact patterns, which presumably lead to altered joint stress. Abnormal joint contact patterns are proposed to develop in part from excessive tibiofemoral rotation (medial rotation of the femur with respect to the tibia), which is exaggerated during movement. Specific aims will test whether or not (1) patellofemoral joint contact area is reduced in magnitude or altered in location in individuals with PFP, (2) there is an association between tibiofemoral rotational alignment, patellofemoral alignment, and patellofemoral joint contact area, and (3) individuals with PFP have increased tibiofemoral rotation motion and moments (torques), in addition to associated altered muscle recruitment during gait activities. Data will be obtained from MRI and instrumented motion analysis (kinematics, kinetics, and EMG) to test these hypotheses.